1. Field
Aspects of the described technology relate generally to a fuel cell stack, and more particularly, to a structure for preventing a membrane-electrode assembly from deteriorating.
2. Description of the Related Art
A fuel cell system includes a fuel cell stack that generates electrical energy using an electrochemical reaction of fuel (hydrocarbonaceous fuel, pure hydrogen, or hydrogen-enriched reformed gas) and oxidant (air or pure oxygen). A direct oxidation fuel cell uses a hydrocarbonaceous fuel in a liquid phase or a gas phase and a polymer electrolyte type fuel cell uses pure hydrogen or hydrogen-enriched reformed gas as fuel.
The fuel cell stack includes a plurality of membrane-electrode assemblies (MEA) and a plurality of separators that are positioned therebetween.
Each membrane-electrode assembly includes an electrolyte membrane, an anode electrode that is positioned on one surface of the electrolyte membrane, and a cathode electrode that is positioned on the other surface of the electrolyte membrane. A fuel channel that supplies fuel to the anode electrode is formed in the separator contacting the anode electrode and an oxidant channel that supplies oxidant to the cathode electrode is formed in the separator contacting the cathode electrode.
When the oxidant supplied to the fuel cell stack is in a non-humidified state or a low humidified state, the regions where the oxidant is first injected into the cathode electrodes, that is, the regions which are closest to the oxidant inlet manifold included in the separators, are operated in a very dry state. That very dry state creates the condition that radicals generated during the operation of the membrane-electrode assemblies can be sustained in the membrane-electrode assemblies for a long time, such that the membrane-electrode assemblies are vulnerable to deterioration.
In particular, since the region in each cathode electrode that is closest to the oxidant inlet manifold has a higher flux and pressure than in other regions, the deterioration of the catalyst layers of respective cathode electrodes is intensified. Once started, the deterioration induces further deterioration, thereby accelerating the deterioration of the membrane-electrode assemblies.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.